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Home , Aphid, Beetle, Biological pest control

Phillip E. Sloderbeck, James R. Nechols and Gerald L. Greene BIOLOGICAL CONTROL OF PESTS ON FIELD IN KANSAS 3 Table of Contents

Conservation of Natural Enemies ...... 5 Importation of Natural Enemies ...... 6 Augmentation of Natural Enemies ...... 6 Important questions to ask when considering an augmentation program ...... 7 Recognition of Common Biological Control Agents ...... 8 Predators ...... 8 Lady ...... 8 Hover ...... 9 Lacewings ...... 10 True bugs ...... 10 Ground beetles ...... 11 ...... 11 ...... 11 Parasitic ...... 11 Tachinid flies ...... 11 ...... 12 ...... 12 Microbial Pathogens ...... 12 Examples of Biological Control of Major Pests of Kansas Field Crops ...... 13 ...... 13 ...... 13 Green bug ...... 14 ...... 15 Russian ...... 15 Chinch bug ...... 15 Corn rootworms...... 17 Conclusions...... 17 Acknowledgements ...... 18 Additional Information on Biological Control ...... 18 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 5 Biological Control of Insect Pests on Field Crops in Kansas Phillip E. Sloderbeck, James R. Nechols and Gerald L. Greene Biological Control In the simplest terms, biological control is the reduction in populations from the actions of other living organisms, often called natural enemies or beneficial species. Virtually all insect and pests have some natural enemies. Learning to recognize and manage these natural enemies can help reduce pests populations and, thus, reduce losses and the need for costly chemical and/or other control measures. Biological control is most effective when used with other compatible practices in an integrated pest management (IPM) program. Practices that are often compatible with biological control include cultural control; planting pest resistant varieties and using selective when other practices fail to keep pest numbers below the economic threshold. To be used effectively, biological control requires a good understanding of the of the pest and its natural enemies, as well as the ability to identify the pest’s life stages in the field. Frequent field scouting also is necessary to monitor natural enemies and evaluate their impact on pest populations. Biological control programs are categorized in three basic ways: conservation, importation and augmentation.

be accomplished by using selective insecticides such as Conservation of Natural thuringiensis (B.t.), timing the application to Enemies avoid periods when important natural enemies would be Conservation of natural enemies is arguably the exposed, or placing the in a location where most important concept in the practice of biological natural enemies will not contact it. In other cases, control and, fortunately, is also one of the easiest to adequately protecting natural enemies may require not understand. Simply put, conservation of natural enemies using an insecticide. means avoiding practices that harm natural enemies and Certain cultural practices also can be detrimental to implementing practices that benefit them. It may sound natural enemies. Plowing, cultivation, mowing or like good common , but the tricky part comes in harvesting operations can be disruptive to natural understanding exactly what practices are harmful and enemies at critical points in their life cycle—if how beneficial practices can be integrated into a detrimental, the practice should be avoided. Excessive production system. This requires understanding the amounts of dust from roads or cultural operations also biology of natural enemies and being willing to modify can reduce control by disrupting the activities of practices to accommodate them. predators and parasitoids. Burning crop residues or The most obvious harmful practice is the use of inappropriately timed also can kill many insecticides at times when natural enemies will be natural enemies. Finally, the ambiguous category of harmed. Insecticides can have direct effects on natural “clean farming,” which includes removing and enemies by killing them, or indirect effects by non-crop , has been found to be detrimental to eliminating their hosts and causing starvation. In some many natural enemies. Increased crop residues have cases, insecticides can be successfully integrated into been shown to favor ground beetles, spiders and other the system without harming natural enemies. This may general predators. 6 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS To better conserve natural enemies, the following Augmentation of Natural questions need to be answered: Where do the natural enemies overwinter? Do they need alternative prey/food Enemies sources to meet their nutritional needs at times when the To many people, biological control means buying pests are not abundant? Do they need shelter during the and releasing beneficial natural enemies to control insect growing season in the form of wooded areas, surface and mite pests. This approach is known as residue, or weedy field borders? Until these questions augmentation. The underlying reason for the wide are answered, the benefits of the natural enemies of any recognition of this technique is that it relies on pest cannot be realized. commercial products which may be advertised in magazines and publicized in the media. Further, the use Importation of Natural Enemies of has trained us to think about pest Many become serious pests when they are management in the context of purchased products. introduced into a new area which lacks their native However, of the three general approaches to insect natural enemies. Examples of European or Eurasian biological control, augmentation is the least sustainable insects that have become important pests on Kansas because it requires the regular or periodic purchase of field crops include the European corn borer, alfalfa products. Nonetheless, in some pest situations it is a weevil, greenbug, Hessian and . highly efficacious, cost effective and environmentally The importation of new natural enemies to control sound approach to pest management. imported pests often is referred to as “classical” The practice of augmentation is based on the idea biological control. Some dramatic successes in that, in some situations, there are not adequate numbers biological control have resulted from importing effective or species of natural enemies to provide optimal natural enemies that are well-adapted to the pest from an biological control, but that the numbers can be increased area where the pest is thought to have originated. (and control improved) by releases. This may require a The goal of classical biological control is to find readily available source of large numbers of natural useful natural enemies, introduce them into the area of enemies. This need has fostered the development of the target pest, and permanently establish them so that companies to produce and sell these organisms. Many they will provide continuing pest control with little or companies (called insectaries) produce a variety of no additional human intervention. Classical biological predatory and parasitic insects; other companies produce control differs from the other general methods and market insect pathogens for use as microbial (conservation and augmentation) because it is not controls. directly conducted by the or . There are two general approaches to augmentation: International agencies, federal agencies (especially the inundative releases and inoculative releases. Inundation Department of [USDA]), and involves releasing large numbers of natural enemies for state agencies (state departments of agriculture and the immediate reduction of a damaging or near-damaging land grant universities) are responsible for identifying pest population. It is a corrective measure; the expected potential target pests, locating their natural distributions, outcome is immediate pest control. Inoculation involves searching these areas for candidate natural enemies and releasing small numbers of natural enemies at intervals, introducing selected natural enemies into the necessary sometimes throughout the period of pest activity, areas. Indeed, there are specific quarantine laws that starting when the pest population is low. In some cases, prohibit private individuals or agencies from introducing the natural enemies will reproduce to provide more non-native organisms (including natural enemies) long-term control. The expected outcome of inoculative without proper authorization from the USDA. Natural releases is to keep pest numbers low, never allowing enemies must be carefully screened by trained personnel them to approach an economic injury level. Therefore, it under rigid quarantine conditions to be certain that is more of a preventive measure. (1) they will provide benefit in controlling the target There are over 100 kinds of commercially available pest, (2) they will not, themselves, become pests, and natural enemies including predatory insects and mites, (3) they do not harbor their own natural enemies that parasitic insects and nematodes, and pathogens. might interfere with their effectiveness or that of other Although this appears to be a large number, it is small natural enemies. Although most are not directly compared to the total number of pests in the United involved in the classical biological control process, they States. Further, many of these natural enemies are can help to conserve or distribute exotic natural enemies specialized for pests on crops such as and that become established. which are not grown in the Midwest. Other BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 7 commercially available natural enemies, such as the reproduce and build up their own numbers during the praying , are of questionable value, even though growing season. This does not preclude the use of they are commonly used by many and some augmentation in field crops. For example, inundative farmers. controls such as and Well-researched applications of natural enemies can, may be cost effective, as can be and do, result in very effective biological control. This inoculative releases that rely on relatively low numbers includes the use of microbial insecticides as well as of natural enemies. Managers should carefully evaluate many specific uses of predators and parasitic insects. the cost of a natural enemy, as with any other production On the other hand, many natural enemies that are sold cost, before making a decision on any augmentative do not control the intended target pest(s). Although the release. reasons for poor control can be very complex, probably the most common cause of these “failures” is a lack of Important questions to ask when knowledge. This includes both a lack of research needed considering an augmentation to make recommendations for successful implementation, and the user’s lack of knowledge about program: the biology of the pests, their natural enemies, and their 1. Has research shown that a release program is environment, all of which are crucial for making effective for the particular pest, crop and local augmentation work. The best advice for pest managers situation? interested in starting an augmentation program is to get 2. Are the proposed release rates sufficient to protect as much information as possible to assure a reasonable crop yields? chance for success. Progress continues to be made 3. When is the best time to release the natural enemy towards developing more user-friendly in relation to the pest’s life cycle? recommendations for effectively using commercially 4. Are releases compatible with the need to apply produced natural enemies. insecticides for other crop pests and with other crop As with any pest management program, the bottom production practices? line of a natural enemy augmentation program is cost. 5. What quality control practices does the company Because of the differences in prices and patterns of use, use to ensure that the natural enemies will be alive it is hard to generalize on the cost effectiveness of and active when released? purchased natural enemies. There is a wide variance in 6. What directions and assistance does the company prices because some natural enemies are much easier provide regarding the handling, release and evalua- and less expensive to produce than others. Inoculative tion of the natural enemy? releases may be less expensive than inundative releases Discuss your pest situation with all available if the timing and conditions are right. Other less obvious Extension personnel as well as with several different factors also have to be considered, especially when companies to obtain the most information about the comparing the release of natural enemies to the use of natural enemy product and pest problem. pesticides. These include resistance management, worker protection, impacts on non-target In summary, Extension personnel receive more pests, environmental considerations and marketing questions about the release of purchased natural enemies practices (such as market differences in conventional than all other approaches to biological control. However, versus organic produce). Another problem is that, for in many cases, it is an area where there are the fewest many commercial natural enemies and their potential answers. It also is important to point out that target pests, there is not adequate research to augmentation cannot be considered “the silver bullet” of recommend specific release rates based upon pest biological control. It is not foolproof, and it requires a population levels. There are, however, many situations certain level of knowledge and understanding to make it where augmentative biological control is cost work. However, augmentation may provide a safe competitive with the use of pesticides or other pest alternative for controlling pests. management practices. On high-value crops, the expense of biological control may be relatively low when compared to overall production costs. On low- value crops, the use of natural enemies must be inexpensive to be justified; or, release numbers have to be low with the expectation that natural enemies will 8 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS Recognition of Common Biological Control Agents Predators Predatory insects and mites live by hunting or trapping other insects (prey), and killing them for food. Over 100 families of insects, spiders and mites contain species that are predaceous, either as adults, immatures or both. About 12 of these families play major roles in the biological control of field pests. Following, are summaries of some of the most important families. Lady beetles Convergent lady Lady beetles or “ladybugs” probably are the most Adults of the convergent lady beetle ( 1 universally known group of beneficial insects. They are convergens) also are about ⁄4 inch long and have orange found almost anywhere and feed on and a variety wing covers that typically have six, small black spots. of soft-bodied insects. Several species are present in However, the number of spots can vary, and some adults Kansas fields, including the following common species. have no spots on their wing covers. The section of the body behind the head is black with white margins and has two converging white lines—from which the species gets its common name. Adults and larvae feed primarily on aphids. Females lay clusters of 10 to 20 yellow on plants infested with aphids. The life cycle is similar to the twelvespotted lady beetle, but this species only has one or two generations each in the Midwest. This species is native to .

Twelvespotted lady beetle

Adults of the twelvespotted lady beetle 1 ( maculata) are about ⁄4 inch long and have pink to light-red wing covers with six black spots on each wing. Both adults and larvae feed on aphids, mites, insect eggs, and small larvae of many insect pests including the European corn borer and alfalfa Sevenspotted lady beetle weevil. Plant and fungal spores also are The sevenspotted lady beetle ( important components of septempunctata) was introduced into North America 3 their diet. Females lay from Europe. Adults are large (about ⁄8 inch), have clusters of 10 to reddish-orange wing covers with seven black spots. 20 yellow eggs on plants. Females lay clusters of 15 to 70 yellow eggs on plants This species has two to Lady beetle eggs that are infested with their aphid prey. Adults also are three generations per predaceous. Adult sevenspotted lady beetles overwinter year in the Midwest and overwinters as large groups of in small groups in , or in litter on the ground adults in litter at the base of trees or along buildings. near the base of plants. BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 9 Some other, smaller, lady beetle species (for legless maggots that range in color from creamy-white example, and ) play an often hidden, to green or brown. They look somewhat slug-like and but nonetheless important, role in controlling field crop are tapered towards the head. The larvae feed on aphids pests ranging from aphids to corn borers. The size and coloration of lady beetle larvae vary some among the species, but generally, they are soft bodied and shaped like a miniature alligator. Newly

Hover fly (or fly) or other insects and move around on the plants in search of prey. They complete their development in two to three weeks while consuming up to 400 aphids each. Lady beetle Some hover fly species pupate on the foliage near 1 hatched larvae are gray or black and less than ⁄8 inch the feeding site, while others leave the plant and enter long. The larvae of most species molt through four the soil to pupate. The is enclosed within a . Later stage larvae can be gray, black, or blue puparium, which is the hardened skin of the last larval with bright-yellow or orange markings on the body. The . The smooth, tan puparia often are teardrop fourth instar larvae consume more aphids than the previous three instars combined. The larvae are not as easy to identify to species as are the adults. Hover flies Hover flies (or flower flies) are common and important natural enemies of aphids, , and other small, slow-moving insects. They have been noticed as predators of small European corn borer and corn earworm larvae, although this is rare. The adults resemble or wasps, and often are seen hovering over . There are many different species that 1 range in size from less than ⁄4 inch long to more than 3 ⁄4 inch long. Many have the typical black and yellow stripes on the that give them a -like Hover fly larva appearance, but others are hairy with a long, thin abdomen. All have short antennae. shaped. Hover flies overwinter as pupae. During the The adults need flowers as and pollen growing season, adults emerge in one to two weeks. sources. They are attracted to weedy borders or mixed Generation time depends on temperature, species and garden plantings that also are infested with aphids. Some availability of food; there may be five to seven flowers that are especially attractive to hover flies include generations per year. wild carrot or Queen Anne’s lace, wild mustard, sweet Hover flies can be effective in suppressing aphid alyssum, coriander, dill, and other small-flowered herbs. populations in gardens and mixed plots. However, Females lay tiny white eggs singly on or compared to other aphid predators like lady beetles and shoots near or among aphid colonies. Each female may green lacewings, hover flies need more aphids to be deposit several hundred eggs through midsummer. The present before they will lay their eggs. Therefore, larvae, which hatch in two to three days, are small, control is best achieved when a variety of natural 10 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS enemies are present. This may partly explain why hover flies are more noticeable later in the growing season after aphid infestations have become established. Because they are not as conspicuous as lady beetle adults or larvae, hover flies may not be given credit for the effect they have on aphid colonies. Their impact on aphids in large commercial plantings, however, has not been studied. At this time, hover flies are not commercially available. Lacewings Lacewings are common predators of aphids and other soft-bodied insects on a wide variety of crops grown in the field and . One of the most Lacewing larva common species is the green lacewing, aphids and other pests in , their usefulness as purchased biological control agents has been limited by insufficient knowledge about release numbers and other technical and biological data. True bugs There are numerous beneficial “true” bugs that are predacious on other insects. This includes bigeyed bugs (Geocoris), damsel bugs (nabids), minute pirate bugs (), and some stink bugs. Unlike many predators

Green lacewing adult carnea. Adults of this species are green in coloration and have large green-veined, clear wings which cover the top and sides of their body. The head has long thread-like antennae, large protruding golden and distinct markings on the face. Adult green lacewings often are seen resting on leaves or in a Predacious stink bug slow, fluttering flight in or above the plant that have chewing mouthparts, true bugs have sucking canopy. Eggs are borne mouthparts. It is common to see these insects with their at the end of a long, thin pointed, -like stalk attached to the Lacewing eggs mouthparts inserted into plant. This stalk may be their prey. These insects 1 will feed on ⁄2 inch or longer. Lacewing larvae, also called aphidlions, feed on aphids, mites, thrips, of various sizes, other and . The larvae actively search plants for soft-bodied insects, and prey, and capture prey in their pincher-like mouthparts. insect eggs. Minute Lacewings that will attack pests on field crops and pirate bugs and stink Damsel Bug nymph other non-arboreal habitats are commercially sold. bugs are available for Although they are extremely important predators of purchase. BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 11 Ground beetles shapes, but the majority are narrow-waisted and - or Ground beetles are commonly found in all -like in appearance. Because of their small size, cultivated crops. Both the larvae and adults are many parasitic wasps are easily overlooked or, if seen, predaceous. Ground beetles likely help to regulate pest appear only as black specks. Most adult parasitic wasps populations. However, their contribution in field crops have wings and can fly to locate new hosts. as compared to other predators has not been well studied. There is some variation in their body shape and coloring, most are shiny and black (some are metallic) and have ridged wing covers. Another characteristic common to ground beetles is a smaller head than thorax, and thread-like antennae. Adults are active at night and tend to hide under rocks or debris during the day. Much of the occurs near the soil surface. Likely targets include caterpillars, root maggots, snails and other soft-bodied insects. Most species do not use their wings, but a few may fly to lights at night. Ground beetles are not commercially available in the United States. Spiders Parasitic wasp attacking aphid While spiders are not insects, they play an important Parasitic wasps reproduce in two basic ways. Most role in the natural regulation of insect populations. As a commonly, females mate with males and the offspring group, spiders are exclusively predaceous, many are made up of both sexes. Unmated females also can specializing on insects. Spiders will feed on a wide produce viable eggs but they are all male. In the second variety of insects including , beetles, caterpillars type of , females do not mate and produce and . There are many groups of spiders all female offspring. The female wasp uses a sword-like commonly found in cultivated fields, some are active , called the “,” to lay its eggs on or searchers; others trap their prey. This is a diverse and inside the host’s body. Wasp larvae hatch and live important group of beneficial insects. parasitically—often hidden from view—eventually killing the host. Larvae develop into pupae in or on the Parasitoids host body, and adults develop from the pupae, Parasitoids are insects that, in the immature stages completing the life cycle. In addition to , of their life cycle, parasitize other insects but have free- females of some wasp species use their ovipositor to living (nonparasitic) adults. Adult parasitoids serve wound a host so that they can feed on its body fluids. mainly to transport their offspring to new hosts. Two Thus, parasitic wasps can kill pests in two ways—by major groups of parasitoids are discussed in this larval parasitism or adult feeding. This adds to their publication: parasitic wasps and tachinid flies. value as biological control agents. Some parasitoids develop individually (one per Parasitic wasps host); while others develop gregariously (two or more Parasitic wasps are the largest group of insects that wasps living on or in the same host). Gregarious serve as biological control agents. They also are the parasitism results when either the adult female wasp most diverse in terms of size, shape and lifestyle. lays more than one ; or when a single egg cleaves Worldwide, it is estimated that there are more than multiple times to create clones (a condition known as 1 million species of parasitic wasps. Almost all insect polyembryony). pests are attacked by at least one species of parasitic wasp, and many are parasitized by more than one Tachinid flies species. Many of these wasps specialize on one target The represents the second largest pest. For these reasons, parasitic wasps are an extremely group of parasitoids and the second largest family of important source of naturally occurring or human- true flies. In North America alone, there are well over managed biological control. 1,000 species, all of which parasitize other insects or Parasitic wasps may be colorful and large (1 to close relatives. Some species of tachinids are colorful 4 inches in length) as adults. However, most are small to (see figure). But most are drab, brownish- or blackish- tiny, dark-colored insects. A few have bizarre body colored insects that closely resemble house flies. In 12 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS general, tachinids are very hairy and this helps to distinguish them from other kinds of flies.

Nematodes potential. Nematodes act as carriers of a kind of bacterium which causes disease in host insects. The Tachinid fly nematodes invade the body of the host larva and then release some from their guts. The bacteria grow Adult females typically glue one or more eggs onto and kill the insect host. The nematodes feed on some of the body of an insect. The resulting larva then bores its the bacteria and dead insect tissue, complete way inside the body of development, and leave the dead host to find new ones. the host insect where it feeds. Some tachinids Microbial pathogens enter the host’s body by parasitize insects, causing disease and being swallowed as the death. These microbial “pathogens” include , insect eats. Larval feeding bacteria, protozoans and fungi. Numerous species in each almost always causes host of these groups serve as important biological control agents death. Therefore, Tachinid fly eggs on armyworm of insect pests. tachinids are very useful biological control agents. Many species occur naturally in North America and others have been imported and released. Pathogens A is a parasitic organism, often a microbe, that causes disease in its host. Typically, pathogens are smaller than their hosts, and usually numerous pathogens infect a single host. Two categories of pathogens are useful as biological controls of insects: nematodes, which are multicellular; and various microbial pathogens, which consist of single cells or subcellular units. Green cloverworm killed by a Nematodes The most commonly used is Bacillus Nematodes that serve as biological control agents thuringiensis. This bacterium is commercially produced are specific to insects and will not harm crop plants. and sold at an affordable These tiny, worm-like occur in nature, but also price. It does not infect are produced in large numbers and sold commercially. natural enemies of field They have the ability to remain active for long periods if crops so it can be used cold-stored, and they can be applied as a spray in combination with suspension much like liquid pesticides. However, other biological sufficient moisture must be present for them to be control agents. effective, and extremes of pH—especially highly Green cloverworm alkaline soil—reduce their survival and control killed by a BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 13 Examples of Biological Control European corn borer The European corn borer is a major pest of corn in of Major Pests of Kansas Kansas and often the target of repeated insecticide Field Crops applications. Several naturally occurring predators are capable of suppressing European corn borer populations Alfalfa weevil in the Midwest. The most prominent of these are various species of lady beetles, the common green lacewing The alfalfa weevil is the number one pest of alfalfa (), minute pirate bugs, hover flies, in Kansas and most other alfalfa production areas of the predatory mites and ground beetles. These predators United States. Like many other U.S. agricultural pests, feed on the egg and early larval stages of corn borers. the alfalfa weevil is not native to this country. Levels of control vary with the year and location, and When the weevil entered the United States, it did so different natural enemy species dominate at different without its natural enemies, which help keep its times. Although several biological control agents have population in check in its native countries. Beginning in been aimed at this pest, none have been completely 1959, the USDA’s Agricultural Research Service began effective at reducing its population below economic levels. importing tiny parasitic wasps from Europe to help control the alfalfa weevil. Five different species of wasps have been imported and released throughout much of the United States. Some of these wasps parasitize alfalfa weevil larvae while others attack the adult . The young wasps feed inside the weevil, destroying it in the process. The wasps complete their life cycles in the host and emerge as adults to seek more alfalfa weevils to continue the cycle. The two dominant species are Bathyplectes curculionis and Bathyplectes anuris, both of which attack alfalfa weevil larvae. In areas where the parasitoids have become established, the need for insecticide applications have been greatly reduced. Farmers need to be aware that most insecticides kill beneficial insects such as parasitoids more readily than weevils. For this reason, Minute pirate bug farmers need to consider an integrated pest management Imported natural enemies include a few species of program that uses a balance of biological, cultural and parasitic wasps and the tachinid fly, Lydella thompsonii. chemical controls. In the early 1900s, Lydella was a very common Growers need to learn how to evaluate weevil and an important biological control agent of damage and become familiar with the economic damage European corn borer larvae. Subsequently, it underwent thresholds in to avoid unnecessary insecticide a decline in the Midwest and elsewhere. This fly has applications. Weevil damage is very conspicuous and been reintroduced into the United States and, in some small amounts of injury may lead you to believe that places, appears to be insecticides are warranted when they are not. having an impact on the Insecticides should only be applied when weevil corn borer. However, populations exceed the established economic thresholds rates of parasitism have so that parasites will be better able to increase in not reached previous numbers—decreasing the need for future chemical levels. Other imported controls. Total levels of parasitism can be estimated, but parasitoids of corn borer only after crop damage already has occurred. Therefore, larvae are the braconid parasitism rates are currently not used when determining wasp, Macrocentrus threshold levels for treatment of the alfalfa weevil. Minute pirate bug nymph grandii and the However, parasitism throughout the season reduces the ichneumonid wasp, Eriborus terebrans. Recent studies numbers of alfalfa weevil larvae and, thus, represents an in Michigan have shown that Eriborus lives longer and important management component for this pest. is more effective near wooded field borders, where 14 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS temperatures are cooler and adult food sources are greenbug host. The parasitized greenbug stops moving available, than in the interior areas of corn fields. More and grabs the leaf with its legs. Movement of the research of this kind is needed to find ways to preserve parasite larva expands and molds the greenbug’s body, and increase the action of native and imported biological giving it a swollen appearance. The parasitoid larva cuts control agents. a hole through the bottom of the greenbug’s body and Current attention is focused on a group of tiny fastens it to the leaf surface with and a glue. The parasitic wasps called Trichogramma. These wasps swollen greenbug cadaver turns a beige to tan color and attack the eggs of the European corn borer and can be is then called a “mummy.” quite effective at reducing corn borer larval populations. However, the trick is to ensure they are present in the proper place at the proper time in high enough numbers to destroy the European corn borer eggs before they can hatch into the damaging larval stage. Several projects are currently underway throughout the United States to improve the efficacy of augmentative releases of Trichogramma. Data suggests that there is a strong relationship between egg mass parasitism and larval population reduction. There also is a high level of variability between parasitoid release rates and egg mass parasitism rates. Thus, one of the key areas of research is to determine the factors that influence parasitism rates, such as environmental conditions, parasitoid release techniques, parasitoid species or strains. Ways Greenbug mummy also must be found to reduce the cost of the parasitoids before augmentative releases of Trichogramma will The parasitoid larva then enters the pupal stage become economically viable on field corn. However, if inside the mummy and the adult parasitoid emerges four research continues, these parasitoids may become a part to five days later. The adult escapes through a circular of the pest management system for corn borer control in hole it cuts in the top of the mummy. The adult the foreseeable future. parasitoid mates and repeats the life cycle by stinging A naturally-occurring protozoan, Nosema pyrausta, additional greenbugs. At a constant temperature of 70°F, infects corn borers and may reduce populations by development from egg to adult requires about 14 days. shortening the adult lifespan and egg-laying period. This Each female adult Lysiphlebus can parasitize about pathogen also has been applied to corn borer 100 greenbugs during her four to five days of life. More populations with some degree of success. It has no important than the death of individual greenbugs is the negative effect on green lacewing predators or the reduction in potential greenbug reproduction. All tachinid fly parasitoid Lydella. However, Nosema is not greenbugs are females which give live to three or compatible with the egg parasitoid Trichogramma four offspring per day. Parasitized greenbugs stop nubilale. Infected Trichogramma have lower survival reproducing within one to five days, while unparasitized rates and a reduced reproductive capacity. The microbe greenbugs reproduce for 25 to 30 days. As a result, Bacillus thuringiensis also has been used as a corn borer parasitism can greatly reduce the rate at which greenbug insecticide that protects other natural enemies. infestations increase. Parasitoid activity in the field can be monitored by Greenbug looking for greenbug mummies on leaves. Weather One of the most important natural enemies of the conditions will largely determine how quickly greenbug is the parasitic wasp, . parasitoids can prevent a greenbug outbreak. Remember This shiny black wasp can be seen on warm, sunny days that aphids that appear healthy may actually have crawling across wheat leaves and stinging (parasitizing) parasitoids developing within, as the mummy stage does greenbugs. The female pierces (stings) the greenbug and not develop until eight to 10 days after parasitism. As a deposits an egg inside. In about two days the tiny egg general rule, a greenbug infestation declines rapidly hatches into a grub which feeds internally on the living once 20 percent of the greenbugs are mummies, because greenbug. The parasitoid becomes mature in about six to at this point most of the living greenbugs are already eight days and then begins to twist and turn inside the parasitized though they have not yet entered the mummy BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 15 stage. This parasitoid is most effective during warm third of Kansas. One of the most promising natural weather from late spring to early fall. Adults are inactive control agents of these pests are predatory mites. at temperatures below 56°F. Other aphids such as the The most common predatory mite in Kansas is corn leaf aphid can serve as an alternate host for this Amblyseius fallacis. It is slightly larger than the Banks parasitoid. grass mite and twospotted , pale brown or Insecticides applied as sprays will kill adult wasps straw colored and ovoid in shape with the head being at and indirectly kill immature parasitoids by killing their the narrow end. They often can be recognized as they greenbug hosts. Methyl parathion and chlorpyrifos move about on the corn leaves in a zigzag pattern as (Lorsban) are more toxic to adult wasps and to immature they search for prey. Other small-sized, naturally parasitoids inside greenbugs than the systematic occurring predators are Stethorus lady beetles, minute insecticides dimethoate and disulfoton (DySyston), pirate bugs, hover fly larvae and predatory thrips. The especially at lower rates. However, the short residual fungal pathogen, Neozygites, also causes mortality to toxicity of methyl parathion allows parasites to spider mites. recolonize a field sooner than when insecticides with Although these mites are very effective in reducing longer residual activity are used. In addition, immature spider mite numbers, they often do not control spider parasitoids inside greenbug mummies gain some populations soon enough to avoid economic damage. protection from insecticides. Higher insecticide rates Studies in have shown that inoculative releases of increase the mortality of immature Lysiphlebus and predatory mites during the growing season could be extend the time before adults can survive on treated useful in controlling spider mites on corn. However, the foliage. The Bayleton, used to control leaf current costs of producing predatory mites precludes on wheat, also is very toxic to adult parasitoids. their commercial implementation. Therefore, more The parasitoid overwinters as a larva and pupa research is needed to develop more efficient ways to inside a parasitized greenbug. Wasps disperse by flying distribute mites into fields and to rear them. Currently, and by being carried as immature parasitoids inside research is being conducted to determine if predatory winged greenbugs. Unfortunately, Lysiphlebus often is mites can be released in the overwintering sites of the attacked by other species of parasitic wasps, which can spider mites so they can move into the corn fields with limit its control of greenbug. the spider mites early in the season; reducing the More research is needed to better define when and numbers of predator mites that would need to be how soon the parasitoid will eliminate greenbug released and the area that would need to be treated. populations and in ways to decrease the lag time between when greenbug populations begin to cause Russian wheat aphid damage and when the parasitoid becomes active. The Russian wheat aphid (RWA) is a new pest of small grains in North America. It is attacked by a Spider mites number of natural enemies already present on other The Banks grass mite, Oligonychus pratensis aphids in the United States and including (Banks), and the twospotted spider mite, Tetranychus predators, parasitoids (parasitic wasps), and pathogens urticae (Koch), are serious pests of corn in the western (mainly disease-causing fungi). Some of the most common predators on RWA are the convergent lady beetle, the common green lacewing, hover flies and chamaemyiid (cammy-my-ee-id) flies. The species of predators that have the greatest impact on RWA depends on location and climate and can vary from year to year. Naturally-occurring parasitic wasps also can attack RWA, but these are not specific to RWA and their impact is not well understood. Two of the species recovered from RWA are and the greenbug parasitoid, Lysiphlebus testaceipes. Parasitized RWAs can be distinguished from other grain aphids based on body shape. The RWA and its parasitized “mummy” are more cylindrical and tapered at both ends than the pear- or oval-shaped mummies of greenbugs Predaceous mite and other grain aphids. The RWA’s antennal length and 16 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS other also are much shorter than those of enemies’ presence and abundance to their impact on other grain aphids. Periodically, fungal infections cause RWA. Some work is currently being done to assess high mortality to RWA. These are most common in predation by lady beetles, parasitism levels based on moist weather and in areas that have generally wet mummies, and the overall impact of natural enemies on RWA in the field. This kind of research will be necessary before biological control can be incorporated into pest management decision-making models. The relationship between RWA density and damage has been determined. Therefore, eventually it may be possible to use presence and abundance data for natural enemies to predict when pesticide applications can be delayed or avoided. However, even in situations where RWAs exceed damage thresholds requiring treatment with insecticides, biological control agents contribute to suppressing and containing the aphid, thereby reducing the likelihood of new infestations and pest outbreaks in wheat and barley fields. One known obstacle to natural enemy effectiveness Russian wheat aphid killed by fungus is that early feeding by RWA causes tillers to roll up tightly. Once enclosed, aphids continue to feed and climates. Infected RWAs can be identified by their reproduce within these protective barriers which prevent fuzzy, sometimes whitish, appearance. This fuzziness is or slow down the entry of most predators and all but the caused when fungal spores coat the dead aphid’s body. smallest parasitoids. The recent discovery that some These spores are carried through the air to other aphids RWA-resistant wheat varieties do not roll their leaves which can then become infected. may allow greater efficacy of biological control agents. No imported predators are known to be established on RWA. However, four species of imported wasps have Chinch bug been collected from parasitized RWA and are believed The chinch bug (Blissus leucopterus leucopterus), is to be established in the United States. All four have been a pest of wheat, corn, sorghum and various grasses, recovered in Kansas. These parasitic wasps represent including and commercial turf. It is an especially two families that are most easily identified by the difficult pest to control in dry when large appearance of the dead aphid mummy, which remains populations occur. Few natural enemies are known to attached to the tillers. Mummies from species in the attack the chinch bug. For this reason, biological control family Aphidiidae are tan or gold-colored and swollen in shape. Mummies from the family are blackish and more flattened. Adults of both families are very small, black insects. Adult Aphidiids are more slender and slightly longer than Aphelinid adults. To date, native aphid predators and parasitoids appear to be having more of an impact on RWA than the imported parasitoids where both are present. Two reasons for this difference are that the newly are not widely distributed, and they are presently much less abundant than most of the native natural enemy species. Sampling RWA is a problem because it often is a sporadic pest that occurs in patches in fields. This is especially the case in the Midwest. However, a on chinch bug sequential sampling plan has been developed for has not been incorporated into IPM programs in the way growers. Determining where and when natural enemies that resistant varieties have. Naturally occurring are active is a more difficult problem. In fact, at the biological controls that do exist include a tiny wasp— present time there is no practical way of relating natural Eumicrosoma beneficum—that parasitizes individual BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 17 eggs of the chinch bug and a few closely related species Conclusions (for example, the hairy chinch bug), and the widespread, nonspecific, fungal pathogen, Beauveria bassiana. As a natural process, biological control plays an Of the two, only B. bassiana seems to serve as a important role in the suppression of field crop pests in natural suppressive agent of the chinch bug. However, it Kansas. It also shows considerable promise as a does not provide consistently high levels of control year management approach for field crop pests. However, to after year. Research has shown that chinch bug infection reach its potential, either as a single tactic, or as a rates are highest when soil moisture is low and component in integrated pest management programs, temperatures are high. However, mortality is greatest research is needed to increase the effectiveness and when these conditions are followed by a combination of predictability of natural enemies and to make biological high temperature, soil moisture and relative humidity. control more economical. Efforts should be continued to Other factors such as availability of overwintering establish new natural enemies for the many foreign pests grasses at field borders, which harbor reservoirs of that affect Kansas field crops. Much work also is needed infected bugs and fungal spores, increase the chances of to find ways to better conserve natural enemies. This natural disease outbreaks in chinch bugs during the next protection extends both to native and imported species, crop season. Higher populations of bugs also help and to those released into the environment as well as spread disease-causing spores. Even with this populations that are already established. Finally, knowledge, at present there are no good predictive improved methods for handling and rearing natural models for forecasting the timing and levels of chinch enemies are needed to increase efficacy and reduce costs bug mortality from B. bassiana. of augmentatively released biological control agents. One step in the right direction would be for farmers who Corn rootworms are interested in using biological control to become Corn rootworms cause extensive losses to corn and more active in working together, and with public other field crops in the Midwest. The most important officials, to promote the research and development of species are the northern corn rootworm (NCR), biological control. longicornus barberi, and the (WCR), D. virgifera virgifera. The western corn rootworm is a major pest in Kansas. Surveys have shown that these pests are relatively free from attack by insect predators and pathogens. However, periodically, certain ant species play an important role by preying on corn rootworm larvae. Predation by ground beetles and soil-inhabiting mites probably occurs; but the effect of these natural enemies on rootworm populations is not well understood. The use of parasitic nematodes to control corn rootworm larvae holds some promise. Nematodes do not have the adverse effect on nontarget organisms (including naturally occurring biological controls) that broad-spectrum insecticides do. Field trials using a center-pivot irrigation application method have shown that high rates of the , Steinernema carpocapsae, were as effective as conventional insecticides in controlling WCR larvae. In addition, parasitic nematodes have been successfully incorporated into pellets that can be conveniently applied to the soil. However, because of the higher cost of nematodes compared to insecticides, and the need to make repeated applications, this pest management procedure is prohibitively expensive on field corn at this time. 18 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS Acknowledgements Losey, J.E., D.D. Calvin. 1995. Quality assessment Our thanks to: Bob Wright, University of Nebraska, of four commercially available species of and Randy Higgins and Gerald Wilde, Kansas State Trichogramma. J. Econ. Entomol. 88:1243–1250. University, for reviewing the manuscript; Anna Barrett Obermeyer, J. 7 R. O’Neil. 1993. Common Natural and Bob Holcombe, Kansas State University, for Enemies. Cooperative Extension editorial and design assistance. For photographs in Service, W. Lafayette, Indiana. addition to contributions from the authors, we thank: Obrycki, J.J. 1995. Know Your Friends: Lady Jack Campbell, University of Nebraska, for the Beetles. Midwest Biological Control News, Vol. 2, convergent lady beetle, lady beetle eggs and greenbug No. 4, p. 3. mummy; Texas A & M Cooperative Extension Service Pickett C.H., F.E. Gilstrap. 1986. Inoculative for the parasitic wasp; Bob Bauernfeind, Kansas State releases of Phytoseiids (Acari) for the Biological University, for the tachinid fly eggs; Tom Harvey, Control of Spider Mites (Acari: Tetranychidae) in corn. Kansas State University, for the lacewing larva and Poinar, Jr., G.O. 1979. Nematodes for Biological eggs; Marlin Rice, Iowa State University, for the hover Control of Insects. CRC Press, Inc. Boca Raton, . fly adult; Ding Johnson, University of Idaho, for the 277 pp. fungal-infected Russian wheat aphids; and the USDA USDA. 1983. Biological Control of the Alfalfa and Clemson University Cooperative Extension Service Weevil. Program Aid No. 1321. for the hover fly larva. Bob Nowierski, Montana State Wintersteen, W. & M. Rice. 1993. Beneficial University, Gary Hein, University of Nebraska, Dave insects in field crops. IPM-34, Iowa State University, Prokrym, USDA–ARS, Stillwater, Oklahoma, provided Ames, Iowa. reprints on the Russian wheat aphid. We also Wright, R.J. 1995. Biological control of insect and acknowledge the use of two slides of unknown origin; mite pests. NebGuide G9501251, University of one from the KSU slide files for the green Nebraska Cooperative Extension Service, Lincoln, lacewing adult; and one from the Southwest Kansas Nebraska. Research and Extension Center for the twelvespotted Wright, R.J. 1995. Achieve lady beetle. Financial support for this publication was by augmenting natural enemy populations. Crop Watch, provided by the USDA–APHIS National Biological University of Nebraska, March, 1995. Control Institute under APHIS Agreement No. 96– 3001–0122–GR. Additional Information on The authors acknowledge the use of the following Biological Control general resources during the development of this publication: Publications Bessing, R. 1995. Know your enemies, but Hoffman, M.P. & A.C. Frodsham. 1993. Natural recognize your allies. Kentucky Pest News, No. 712, p. Enemies of Vegetable Insect Pests. Cornell Cooperative 7. University of Kentucky, Lexington, Kentucky. Extension Service, Ithaca, . Higgins, R.A., S.L. Blodgett & A.W. Lenssen. Mahr, D. & N. Ridgeway. 1995. Biological Control 1989. Alfalfa weevil management in Kansas: II. Non- of Insects and Mites: An Introduction to Beneficial chemical controls. Entomology 115. Cooperative Natural Enemies and Their Use in Pest Management. Extension Service Publication No. MF-918, April 1989, North Central Regional Publication No. 481, University Manhattan, Kansas. of Wisconsin, Madison. Knutson, A., E. Boring, G. Michels & F. Gilstrap. McCoy, C.W. 1987. Microbial Agents for Use in 1993. Biological control of insect pests in wheat. Integrated Pest-Management Systems. Southern B-5044 Texas Agricultural Extension Service, College Cooperative Series Bulletin 318, Arkansas Agricultural Station, Texas. Experiment Station, Fayetteville. Legg, D.E., G.L. Hein & F.B. Peairs. 1991. NCS-3 Committee. 1996. Integrated Pest Sampling Russian wheat aphid in the Western Great Management: A Sustainable Approach. North Central Plains. GPAC-138, Colorado State University Regional Publication No. 586, Iowa State University, Cooperative Extension Service, Ft. Collins, Colorado. Ames, Iowa. Levine, E & H. Oloumi-Sadeghi. 1991. Management of Diabroticite rootworms in corn. Annual Internet Review of Entomology 36: 229–255. Midwest Biological Control News http://www.wisc.edu/entomology/mbcn/mbcn.html 2 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS

Phillip E. Sloderbeck, Professor and Extension Specialist, Entomology, Southwest Area Extension Center; James R. Nechols, Professor, Research and Teaching, Entomology, Manhattan; Gerald L. Greene, Professor and Entomologist, Southwest Research Center

Cooperative Extension Service, Kansas State University, Manhattan

MF-2222 August 1996 Issued in furtherance of Cooperative Extension Work, acts of May 8 and June 30, 1914, as amended. Kansas State University, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Richard D. Wootton, Associate Director. All educational programs and materials available without discrimination on the basis of race, color, national origin, sex, age, or disability. File Code: Entomology—2 AB 8-96—5M